1. Field of the Invention
The present invention relates to methods and apparatus for identifying features in an image. More particularly, but not exclusively, the present invention relates to methods and apparatus for fitting models to an image to identify features in the image.
2. Description of the Related Art
Automated image analysis may be used to reduce manual workloads in determining properties of images. Image analysis is used in a variety of different fields to identify features of images. One area in which image analysis techniques are used is to process medical images where the identification of anatomical features in an image can provide useful information to medical practitioners.
Projection imaging techniques are commonly used to generate medical images in which electromagnetic radiation that can penetrate a solid object, such as X-rays, is generated and projected through an anatomical region of interest. A sensor is arranged to detect the electromagnetic radiation after passing through the anatomical region of interest. The anatomical region of interest attenuates the electromagnetic radiation based upon its density and composition and as such the electromagnetic radiation detected by the sensor is indicative of the composition of the anatomical region of interest. The resulting two-dimensional image represents the cumulative attenuative effect of the density and composition of the anatomical region of interest and can therefore be analysed, either by a human or automatically. However it will be appreciated that analysing two-dimensional images such as X-ray images only provides a limited amount of information.
Imaging techniques such as X-ray Computed Tomography (CT) and Magnetic Resonance (MR) imaging are able to provide three-dimensional information for analysis. MR images are obtained using powerful magnetic fields to align the magnetization of atoms of the anatomical region of interest and are expensive to generate. CT images are generated from a large amount of X-ray data captured at a number of different angles through an anatomical region of interest which is processed using tomographic imaging techniques. CT imaging techniques are also expensive and additionally require exposure of a patient to a large amount of X-ray radiation which is undesirable.
A cost effective three-dimensional imaging technique is therefore desirable.
It is an object of some embodiments of the present invention to obviate or mitigate at least some of the problems set out above.